Method and apparatus for testing embedded cores

Abstract

The inputs to an embedded core, e.g., the core terminals, may not be directly connected to pins on the SoC. The lack of direct access to an embedded core's terminals may complicate testing of the embedded core. A test wrapper including boundary scan test (BST) cells may be used to test an embedded core. Dual function BST/ATPG (Automatic Test Pattern Generation) cells may be used to perform both BST and ATPG tests on embedded cores.

1. Apparatus comprising:
 a scan cell operative to function as a capture storage element in a boundary scan test mode, the scan cell having a data input node, a clock input node, a scan in input node, and an output node; 
 an update storage element having an output node and an input node coupled to the output node of the scan cell; 
 an input multiplexer coupled to the data input node of the scan cell, the input multiplexer operative to select between a functional input and a boundary scan test input; 
 a clock multiplexer coupled to the clock input node of the scan cell, the clock multiplexer operative to select between a boundary scan test clock signal and a system clock signal; and 
 an output multiplexer operative to select between the functional input, a signal from the scan cell output node, and the update storage element output node for output. 
 
   
   
     2. The apparatus of  claim 1 , wherein the input multiplexer is operative to select in response to a data register signal. 
   
   
     3. The apparatus of  claim 1 , wherein the clock multiplexer is operative to select in response to a test mode select signal. 
   
   
     4. The apparatus of  claim 1 , wherein the output multiplexer is operative to select in response to a test mode select signal. 
   
   
     5. The apparatus of  claim 1 , wherein the output multiplexer comprises a three-input multiplexer. 
   
   
     6. The apparatus of  claim 5 , wherein:
 the functional input is received on a first input of the three-input multiplexer; 
 the signal from the scan cell output node is received on a second input of the three-input multiplexer; and 
 the update storage element output node is connected to a third input of the three-input multiplexer. 
 
   
   
     7. The apparatus of  claim 1 , further comprising a line connecting the output node of the scan cell to an input of the output multiplexer.